Two-stroke internal combustion engines are used for a variety of applications despite their relatively high fuel consumption and exhaust gas emission rates. As concern for the environment increases, government regulations have been and are being promulgated requiring reduced emissions and improved fuel economy from two stroke internal combustion engines.
One method used to lower the emissions and fuel consumption of four stroke internal combustion engines has been the adaptation of electronically controlled and electro-magnetically actuated fuel injectors as opposed to carburetors to provide fuel to the engine. These fuel injectors can be precisely timed to deliver metered quantities of fuel to the engine at the appropriate times to reduce emissions and fuel consumption and have therefore been widely used. However, the electronic control unit, sensors and fuel injectors add considerable cost and complexity to the system and are too expensive and impractical for many small engines systems which do not have a battery or generator to power and control the electronic fuel injection systems.
Another approach to lowering the fuel consumption and emission rates of internal combustion engines is by direct injection of the fuel into the engine cylinder as opposed to an intake manifold of the engine which allows better timing of the injection to reduce fuel losses in the exhaust scavenge gas thereby reducing hydrocarbon exhaust emissions and decreasing the fuel consumption of the engine.
In some proposed systems, as in U.S. Pat. No. 5,271,372, a fuel injector delivers fuel, usually at a relatively low pressure, to a compression chamber wherein the fuel is mixed with air creating a pressurized mixture which is injected directly into the cylinder of the engine. While these systems can be effective at reducing fuel consumption and emissions from the engine, they are relatively expensive due to the fuel injector and the overall complexity of the fuel injection systems and also increase the size of the engine as the compression chamber is located on top of the cylinder head with the fuel injector mounted adjacent to the compression chamber. This is undesirable for small engines such as those used in lawn and garden equipment, boat motors and small motorcycle engines where a compact and inexpensive engine is required.